Aluminum alloy containing lithium



Patented Mar. 8, 1927.

JOHANN CZOCHRALSKI, OF FRANKFORT-ON-THE-MAIN,

"* V ATENT GERMANY, ASSIGNOR, BY

MESNE ASSIGNMENTS. T ALLIEDPROCESS CORPORATION, OF NEW YORK, N. Y-, A

CORPORATION OF NEW YORK.

ALUMINUM ALLOY CONTAINING LITHIUM.

No Drawing.

My invention relates to aluminum alloys containing lithium. ol' the type described in' application Scr. No. 302,404, filed June 28, 1920, by myself and George Welter. Al- 5 loys of this type are especially adapted for mechanical or constructional purposes, partieularly if they have been subjected to suitable heat treatment.

I have discovered that the hardening of aluminum drydithimn can be produced by the addition of exceedingly small quantities of lithium, such as from mere'traccs up to one-hall of one per centum.

By adding other metals it is possible to further improve the qualities of the aluminum alloys containing lithium. The effects produced depend upon the metals used.

Thus, it the alloys areto have ahigh tensile strength as-well as ductility and great capacity for clongation,'zinc or tin should be added. Such an alloy, especially suited for the manufacture of sheets comprises zinc, 8 to 12%, lithium, from more traces up to 0.5%, and the rest aluminum.

The zinc can, in this alloy, be wholly or partly replaced by tin.

If the main desideratum is an alloy having a high tensile strength with less ductility and capacity for elongation, then other metals should he added. high tensile strength may have advantageously the following composition: zinc, 1 to 12%; copper, up to 4%; lithium, from a trace up to 0.5%.

In this alloy, the copper may be wholly or partly replaced by nickel, cobalt, manganesc, tin, chromium, or silver.

These alloys may be made by melting in a crucible the pure aluminum. and then adding the copper and/or other metals, either separately or in the form of-previously made alloys. The crucible is then removed from the furnace and the lithium metal added, preferably by enclosing it in an aluminum jacket, and submerging it under the surface of the molten metal.

Products such as rods, bars, wire, sheets, shapes of all kinds, rivets, etc., can be made from such. aluminum alloys b pressing, rolling, forging, drawing, orot er such opera! tions. These products can be 'greatly improved it after-they have been manufaccontaining 8% onmore of silicon. My al- Thus, an alloy of Application filed December 7, 1923. Serial No. 679,262.

tured, they are subsequently subjected to a heat-treatment which consists in heating them to a temperature above 100 C. and then permitting them to cool slowly or rapidly chilling them. It is not possible to specify a definite maximum temperature for this heating but it should not in general be above 500 C.) as it varies according to the composition of thealloy, and can read- 11y be determined by test for each particular alloyf So also, the characteristics of the product as to tensile strength or elongation can be varied according to' the manner of 5 cooling. Rapid chilling tends toproduce alloy products of higher tensile strength, while y slow cooling, alloy products capable of greater elongation and ductility are obtained. f

The cooling or chilling may be carried out m an oil or water bath, in an air current,

or in any other suitable medium. The temperature of the cooling medium ma be varied according torequirement; an the heat-treatment may be repeated if necessary or desired.

I am aware of the patent to Pacz, No. 1,387,900, patented Aug. 16, 1921, which describes an alloy of aluminum and silicon,

loy contains no silicon except perhaps that small amount which sometimes occurs as an impurity in commercially pure aluminum. My alloy is therefore substantially free 'from silicon.

Ielaim:

'1. The .hereindescribed alloy consisting predominantly of aluminum and substantially free from silicon, and containing an appreciable amount of lithium in less pro: portion than one-half of orie per centum.

2. The hereindescribed alloy consisting predominantly of aluminum, with a minor proportion of a metal having the properties 'hereinabove described of zinc and tin, and

containing an appreciable amountof lithium in less proportion than one-half of one per centum. 3. Aluminum alloys containing zinc, 1 to 12%; lithium in quantity varying from a trace to one-half .of one percentum and thebalance chiefly aluminum. 4. Alloys according to claim 3 containing up to 4% of additional alloying metal whose presence tends to increase the tensile strength of the alloy.

5. Alloy according to claim 3, containing up to 4% of copper.

6. Articles of manufacture made from an aluminum alloy containing zinc, 1 to 12%, lithium in quantity varying; from a trace to one-half of one perccntum and the balance chiefly aluminum, which articles have been subjected to a heat-treatment comprising the ste 75 of heating to a temperature above 100 and then cooling them.

7. Articles as claimed in claim (3 in which the alloy contains up to 4% of an additional alloying metal whose plcscncc tends to increase the tensile strength of the alloy.

8. Articles as claimed in claim 6 in which the alloy contains up to 4% of copper.

In testimony whereof, I aflix my sigma 20 ture.

J OHANN CZOCHRALSKI. 

